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| janek |
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Posts: 413 Joined: 14th Nov 2004 Ride: 2000 AU II Fairmont Ghia Location: Brisbane Most of the time/Sydney Some of the time |
For those of us privelaged enough to have a ba or au vct, do ANY of the aftermarket ems systems have this feature? or is it not ecu controlled?
What about Megasquirt? i have been reading into it a fair bit, and new functions seem possible... would it be? im looking at buying my ecu at some stage in th enest 1-3 months, just as soon as i get my exhaust done
_________________ Organza 2000 AU 2 Fairmont Ghia
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| Hyena |
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I was actually thinking about aftermarket ECU's and VCT the other day.
What does VCT actually do and how ? Obviously it's variable cam timing, but I would have thought playing with the timing up and down with an aftermarket ECU or chip would have much the same effect and VCT anyway ? I don't know about EMS, but Shugg has VCT and is running it with a haltech interceptor.
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| Spork |
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Well it changes when the valves are opening. Earlier or later. I suppose this would be an RPM / throttle related thing to optimise cylinder filling.
On the BA's you could have seperate control of each cam to adjust valve overlap too but I think they just move together at the moment. I believe the system works by mounting the cam on a helical gear and applying oil pressure to each side. As the helical gear moves in and out the cam is rotated relative to the timing chain gear. There would be one or more solenoids for oil control that would require varible duty cycle signals. There might also be a position sensor required for feedback control. Also as far as I know only the motec M400 - M800 range can control aftermarket VCT. The VTECH option you see on some is something different and is only a switch on/off thing. Pretty sure you couldn't do this with MegaSquirt but if you've got an idea please share it.
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| Waggin |
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Yep, definantly an option on the Motec Mx00's, but you have to pay extra to get it enabled
_________________ WAG363: AUII LTD Supercharged 363 Dart Stroker [Supercharged 363 LTD Build] |
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| janek |
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Posts: 413 Joined: 14th Nov 2004 Ride: 2000 AU II Fairmont Ghia Location: Brisbane Most of the time/Sydney Some of the time |
i thought it was like you said an oil pressure related thing, but operated on an rpm/load switch?
if so, i am sure it wouldnt be all that difficult to devise something hat triggers at + x000 rpm, if load is + xx% or am i wrong again, and oversimplifying the ecu control over it? i dont neccessarily want to control the vct, just enable it... the solenoid @ the front of the engine has, i think, only two wires running to it... anyone have detailed au manuals or anything to shed us some light?
_________________ Organza 2000 AU 2 Fairmont Ghia
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| Disco Frank |
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vtech is actually a 2nd cam for the inlet/exhaust valves
soa dohc car r has 8cams! and the vtech on the ba's run at the same time
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| Bert |
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VCT is controlled by a solenoid. The AU just switches it ON and OFF, there is no PWM. I believe the F6 Typhoon does use PWM on both cams. Only the Motec I know off can do PWM of the cam phasing properly.
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| janek |
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Posts: 413 Joined: 14th Nov 2004 Ride: 2000 AU II Fairmont Ghia Location: Brisbane Most of the time/Sydney Some of the time |
hmm.. so in theory, the vct adds approx 5% to the power of the engine, with a modded engine, theoretically it will do more again, correct?
i thought it was just a solenoid 
in that case, aftermarket ecus shouldnt be an issue!
_________________ Organza 2000 AU 2 Fairmont Ghia
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| janek |
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Posts: 413 Joined: 14th Nov 2004 Ride: 2000 AU II Fairmont Ghia Location: Brisbane Most of the time/Sydney Some of the time |
and for the noobs, what is PWM?
_________________ Organza 2000 AU 2 Fairmont Ghia
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| Bert |
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PWM, Pulse Width Modulation. If you cycle a soleniod On then Off for .5sec each respectively in a continuous cycle you are Pulse Witdth Modulating the soleniod at a 50% duty cycle. Half the time on and half the time off. The solenoid plunger will normally take some position other than fully closed or fully open and act like a electrically controlled valve. This is how AFAIK all electronic boost controllers work.
The best way to use this is in a Closed loop Feedback System. The cam phasing (in this case) would be used as the main input into the system. Then from this all you have to do is make up a "map" of desired retard or advance wrt to RPM and load. The control system in this case the ecu would "target" your map. My reasoning on this is that the oil pressure changes due to many factors, biggest being temperature. Your cam phasing should therefore be correct at all times. Most people/tuners just do 2 power runs on a dyno, one with cam phasing on and the other off. Overlay the 2 runs and then just switch the soleniod at the crossover point. To make a cam phasing map wrt to RPM and load would require time, dyno and some real brains. Something I believe most public/mainstream tuners don't have. P.s wrt, with respect to |
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| Shugg |
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janek wrote: hmm.. so in theory, the vct adds approx 5% to the power of the engine, with a modded engine, theoretically it will do more again, correct?
I havent read the whole thread, but forget about theory. I have run my car on a dyno with the VCT connected and without it connected. I made extra 5rwkw power without it connected because the AFR was adjusted without the VCT kicking in. The VCT only enable's a smoother ride, it doesnt give you any more power as such. |
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| Bert |
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Shugg wrote: janek wrote: hmm.. so in theory, the vct adds approx 5% to the power of the engine, with a modded engine, theoretically it will do more again, correct? I havent read the whole thread, but forget about theory. I have run my car on a dyno with the VCT connected and without it connected. I made extra 5rwkw power without it connected because the AFR was adjusted without the VCT kicking in. The VCT only enable's a smoother ride, it doesnt give you any more power as such. Was the 5kw gain at peak or was the curve actually better? You are correct in a sense, the VCT is not supposed to give more peak power BUT a better power curve. Also it is very easy to improve the factory's tune. I am already getting 600km out of my NC fairlane with a 70% highway/30% city driving with no wideband and just seat of the pants tuning. At the current rate it uses fuel I predict 750km of only highway. Advancing the cam will move the torque curve slightly earlier, retarding the opposite. When I do engines for my mates and put in a cam I always install it advanced. How far depends on the cam and requirements. |
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| Shugg |
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Bert wrote: Was the 5kw gain at peak or was the curve actually better? You are correct in a sense, the VCT is not supposed to give more peak power BUT a better power curve.
I didn't actually notice the power curve with the VCT disconnected. The 5 extra rwkw's was made at peak power because it ran richer without the VCT. I find that my VCT is just a hinderance at time's anyway. I have a fully re-built high compression engine. VCT's are just a hastle to get power out of. There is a dyno chart in my gallery (VCT connected), it will show you what peak power/torque curve she is producing. I only get 450km's out of a tank, combined city, country and hooning 
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| tjb45 |
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I know Rank Rotary in Melbourne have installed a Wolf3d with a BA XR6 Turbo engine, controlling both variable cams. Might be worth giving them a call..
Good luck |
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